Search PubMed⌕ Search

Biomedical subjects

H Abe

Publications and source records attributed to H Abe.

At least 1,423 records · Page 79Linked to original sources
PubMed1983

Randomness of the process of protein folding.

How specific or definite are pathways of folding and unfolding in globular proteins? In order to study this question, computer simulation of the folding-unfolding transition was carried out in a two-dimensional lattice model of proteins in which it is assumed that strongly specific intramolecular interactions contribute to the stability of the native conformation. This specificity of the interactions should tend to make the pathways of folding and unfolding more definite than reality. Yet, the analysis of the record of simulation indicated the process of transition to be stochastic rather than definite. This poses a fundamental problem of how to describe the pathways of folding and unfolding transition. It is argued that the description should consist of (i) a definition of intermediate states in terms of characteristic conformational features and (ii) stochastic rules of transitions between these intermediate states. The simplest would be the case in which the transitions occur as a markoffian process.

Kinetics↗
PubMed1983

The effects of vasopressin on electrical activity in the guinea-pig supraoptic nucleus in vitro.

Brain slices of the guinea-pig hypothalamus were used to determine the effects of vasopressin on intracellular potentials in neurones of the supraoptic nucleus. Vasopressin (0.05-1 i.u./ml.) depolarized the membrane without apparent change in the input resistance and decreased the spontaneous firing rate. This action of vasopressin was retained in the medium containing 0 mM-Ca2+, 12 mM-Mg2+ and 0.3 mM-EGTA. Amplitude of the vasopressin-induced depolarization was voltage-independent. Ion-substitution experiments showed that the changes in [K+]o, [Cl-]o and [Ca2+]o had little effect upon the amplitude of vasopressin-induced depolarization, whereas the depletion of [Na+]o slightly reduced the amplitude. The vasopressin-induced depolarization was blocked at a temperature of 15 degrees C and by ouabain in a dose of 10(-4) M. Dibutyryl cyclic AMP (2 mM) produced electrophysiological effects similar to those seen with vasopressin, and actions of both agents were potentiated by either papaverine (10(-4) M) or theophylline (10(-2) M). Contents of cyclic AMP in tissues incubated with vasopressin were significantly higher than in cases of incubation with normal Krebs solution. We conclude that vasopressin directly modulates the activity of supraoptic neurones, possibly through activation of adenylate cyclase.

Action Potentials↗
PubMed1983

Hemodynamics in Shy-Drager syndrome and treatment with indomethacin.

Hemodynamic studies were performed in a case of Shy-Drager syndrome with severe orthostatic hypotension. Marked depression of blood pressure was recognized immediately after the tilt-up, wherein decrease in cardiac output was detected (65 leads to 35 ml; stroke volume) during measurements by echocardiography. In association with the depression of blood pressure and decrease in cardiac output, Doppler sonograms showed the overall blood flow reduction in the brain-supplying arteries, suggesting some breakdown of autoregulation of the cerebral blood flow. Medication with indomethacin obviously limited the depression of blood pressure during the standing exercise. The pressor mechanism of indomethacin might be regarded as a result of increased vasoconstrictivity by inhibiting the synthesis of prostaglandins.

Autonomic Nervous System Diseases↗
PubMed1983

Influence of mesangial proliferation on posturally induced change in glomerular filtration rate.

The effect of the change from supine to upright position on GFR (measured by creatinine clearance) was studied in nonazotemic patients with biopsy-proven primary glomerulonephritis. Compared to healthy subjects, the fall in GFR following the postural change was significantly larger in patients with mesangial proliferation (MP) and with both MP and thickening of glomerular capillary wall (GCW), while similar in those with thickening of GCW alone, suggesting that MP, but not thickening of GCW, augments posturally induced fall in GFR. The augmented fall in GFR in patients with MP was accompanied by larger fall in GFR per unit increase in plasma renin activity than in healthy subjects, and was eliminated by angiotensin-converting enzyme inhibition. We conclude that MP augments posturally induced fall in GFR through affecting glomerular reactivity to angiotensin II.

Adolescent↗
PubMed1983

Transient collateral augmentation during coronary arterial spasm associated with ST-segment depression.

To examine the possible existence of collateral circulation during coronary artery spasm, we attempted to visualize the transient appearance of collateral vessels that could serve to salvage otherwise jeopardized ischemic areas. In three patients with vasospastic angina, total spastic obstruction of a major coronary artery was associated with transient collateral augmentation, which was supplied by the nonspastic artery during anginal period associated with ST-segment depression. These collateral vessels disappeared when the angina and ST changes resolved after nitroglycerin administration. These findings suggest that the collateral blood supply could transiently occur through preexisting vessels to perfuse the ischemic area during coronary artery spasm and that such collateral flow could have a role in preventing transmural myocardial ischemia, resulting in a lesser degree of ischemia associated with ST-segment depression.

Adult↗
PubMed1983

Noninvasive evaluation of pulmonary hypertension by a pulsed Doppler technique.

We used a pulsed Doppler technique to examine the flow velocity pattern in the right ventricular outflow tract in 33 adults. In the patients with normal pulmonary artery pressure (mean pressure less than 20 mm Hg, 16 patients), ejection flow reached a peak level at midsystole (137 +/- 24 msec, mean +/- SD), producing a domelike contour of the flow velocity pattern during systole. In contrast, the flow velocity pattern in patients with pulmonary hypertension (mean pressure greater than or equal to 20 mm Hg, 17 patients) was demonstrated to accelerate rapidly and to reach a peak level sooner (97 +/- 20 msec, p less than .01); in 10 of the pulmonary hypertensive patients a secondary slower rise in flow velocity was observed during a deceleration, resulting in the midsystolic notching. The time to peak flow (acceleration time, AcT) and right ventricular ejection time (RVET) were measured from the flow velocity pattern. Either AcT or AcT/RVET decreased with increase in mean pulmonary artery pressure, and a very high correlation (r = -.90) was found between AcT/RVET and log10 (mean pulmonary artery pressure). The use of this technique permitted the noninvasive estimation of the pulmonary artery pressure.

Adolescent↗
PubMed1983

Human growth hormone and somatomedin C suppress the spontaneous release of growth hormone in unanesthetized rats.

To investigate the feedback control of GH secretion, we examined the effects of human GH (hGH) and somatomedin C (SmC) on spontaneous GH secretory surges in unanesthetized, freely moving rats. Under pentobarbital anesthesia a right atrial catheter and an intracerebroventricular cannula were placed 7-10 days before the experimentation. For iv studies, hGH (0.3 U/ml.h) was infused for 6 h after an iv loading dose (0.3 U) at the beginning of the experiments. For intraventricular injections, hGH (0.1 U/10 microliter) or SmC (500 ng/10 microliter) were injected into the lateral ventricle 2 h before the experiments. The equivalent dose of crystalline BSA diluted in the same vehicle solutions was administered to the same rat as a control on a separate day. Venous blood samples were collected every 20 min for 6 h. Intravenous and intraventricular administration of crystalline BSA did not affect the typical rat GH (rGH) surges which appeared about every 3 h and reached peak values of more than 300 ng/ml. The iv infusion of hGH significantly inhibited the amplitude of rGH surges compared to controls (planimetric areas under the secretory profile 752 +/- 172 vs. 1921 +/- 183, P less than 0.01, n = 6). rGH secretion was similarly inhibited by intraventricular hGH (701 +/- 127 vs. 2208 + 225, P less than 0.01, n = 6) and by intraventricular SmC (537 +/- 70 vs. 1503 +/- 114, P less than 0.01, n = 6). These findings suggest that both GH and SmC are active in the feedback regulation of rGH secretion.

Animals↗
PubMed1983

Arteriographic features of angina pectoris associated with ST segment depression during coronary arterial spasm.

To examine the angiographic features of vasospastic angina associated with ST segment depression, we attempted to analyze the coronary arteriograms of 12 patients who exhibited ST segment depression during the ergonovine provocative test. Right and left coronary arteriograms were obtained successively within a short period when the ergonovine administration revealed ST segment depression. Eight out of 12 patients showed non-total spastic obstructions in one of the major coronary arteries. Among them, a collateral augmentation was found only in one patient. Two cases exhibited the well-developed collateral channels during non-anginal periods and in one case a collateral blood supply was reduced by the spasm occurred in the donating artery. In another one, the collateral circulation did not change during anginal period. Three out of 4 patients who showed total spastic obstructions demonstrated transiently augmented collateral circulation which was supplied by the non-spastic artery. These findings may indicate that ST segment depression during coronary artery spasm could attribute to a subendocardial ischemia caused by an incomplete occlusion of large coronary artery and transient reduction or augmentation of collateral blood flow.

Adult↗
PubMed1983

Semi-supervised exercise training program for patients with coronary heart disease--its effectiveness and possible diagnostic implications for predicting their severity.

Semi-supervised physical training for 12 weeks was performed on 60 patients with coronary heart disease including 48 patients with myocardial infarction and 12 with angina pectoris. The training program consisted of medically-supervised training at the institute once a week and unsupervised training at home at least twice a week with an intensity of 70 to 85% of the maximum heart rate which had been attained by a symptom-limited multiphasic treadmill stress testing according to Bruce's protocol. The results showed an average increase of maximum oxygen consumption from 27.0 +/- 5.7 to 31.0 +/- 7.8 ml/min X kg (p less than 0.01) and of treadmill time from 507 +/- 120 to 673 +/- 140 sec (p less than 0.0001). Cardiovascular responses reduced at a submaximal level of exercise and remained unchanged at the maximal level of exercise. No detrimental events were encountered during the program. The left heart catheterization and coronary angiogram were performed on 35 out of 60 patients. The trainability was higher in patients with single-vessel disease than in those with multi-vessel disease. Based on these results, supervised training should be required mostly for patients with low physical fitness, and patients with high physical fitness can probably improve their physical abilities by self-training at home following a proper exercise program.

Adult↗
PubMed1983

Ultrastructural study on the granule-containing cells in the rat autonomic ganglia.

In the rat superior cervical ganglion, small granules, 100-150 nm in diameter, and large granules, 80-280 nm in diameter, were seen in the granule-containing (GC) cells. Most GC cells contained almost exclusively the small granules (SG type cell), while a few cells almost exclusively the large granules (LG type cell). The GC cells formed both efferent and cholinergic afferent synapses. The efferent synapses were about four times as many as the afferent ones. In the major pelvic ganglion of rats, SG type and LG type cells were present in comparable numbers. Cells with both types of granules were also noticed. Ovoid-shaped granules, 60 X 140 nm with a core of moderate electron density, were observed in some SG type cells. Both afferent and efferent synapses were noted on GC cells in this ganglion. The latter were more numerous than the former. SG type cells formed more synapses than LG type cells. Based on these observations, the physiological significance of GC cells was discussed.

Animals↗
PubMed1983

Evidence of beneficial effects of strict glycemic control on diabetic vascular complications--a prospective study with artificial devices.

This prospective study was undertaken to examine whether glycemic normalization could have beneficial on the course of diabetic vascular complications in 6 insulin-dependent diabetics. A significant amelioration of glycemic regulation was achieved by intensive glycemic control with artificial devices and multiple injections for 3 months, which also resulted in an improvement in conduction velocity, a regression in retinovascular permeability and a decrease in urinary total protein excretion. These results indicate that even after short-term treatment, glycemic near-normalization can have a beneficial effect on the early stage of diabetic vascular complications.

Blood Glucose↗